One of the most important tasks facing psychiatry is the development of objective measures that can aid in diagnosis, treatment selection, and evaluation of therapeutic response. Disturbances in psychomotor activity are cardinal features of depression, mania, and attention-deficit hyperactivity disorder. During the last few years microprocessor controlled monitors have been developed that can precisely record activity levels in ambulatory patients throughout the day and night. The overall aim of this application is to obtain accurate, minute-to-minute, activity recordings in patients with major mood disorders and attention-deficit disorder, to develop more precise objective indices of hyperactivity, agitation and psychomotor retardation. Furthermore, fundamental data will be collected on the rest-activity patterns of normal controls, normal adults with first degree relatives with major psychiatric illness, unmedicated children with attention-deficit hyperactivity disorder, and adolescents, adults, and geriatric patients with various forms of depression. These records will be analyzed by computer to reveal the underlying temporal structure of the data. This will enable us to test several chronobiological theories that postulate that mood disorders may be due to defects in our biological clocks. Three types of major defects have been proposed in this study. In the first instance, the patients rest-activity rhythm may be overly controlled by internal clocks, and may thus lack flexibility and adaptability. We hypothesize that this situation can occur in children with attention-deficit disorder, and may be responsible for their difficulty adjusting their activity level to meet the demands of their environment. In the second instance the rest-activity rhythm may be insufficiently ordered. This may occur in patients with seasonal affective disorder. It is possible that their rest-activity pattern may no longer be entrained to a 24 hour day because they are receiving insufficient light cues, and phototherapy may correct this defect. In the third instance, there may be a change in the pattern of activity, with an increase in harmonic frequencies. Thus, 12 hour harmonic rhythms may be observed in certain patients with affective illness. We postulate that this 12 hour rhythm is a chronobiological correlate of the clinical concept of diurnal variation, and may serve as an important biological marker for affective illness. The overriding objectives of this study are to mathematically identify the alterations in locomotor activity levels and rhythms that occur in these psychiatric disorder, and to ascertain the effects of treatment on these patterns. With this information objective instruments may be developed that can aid in psychiatric evaluation, and in the monitoring of therapeutic response. Thus, these studies may help provide tools to facilitate the objective diagnosis of attention deficit hyperactivity disorder in children, and the assessment of unipolar and bipolar depression in adolescents, adults and geriatric patients.